What’s the point of

occupational exposure limits? John Cherrie

Summary…

• OELs, the essence of occupational hygiene

• Legislative tools - compliance

• OELs in crisis – do they really work to protect the health of

workers?

• Things just keep getting better

• A new paradigm – Kaizen

Lead poisoning

Nicander of Colophon (130 BC)

described the effects of several

poisons, including the effects of

lead

Waldron, H A. 1973. “Lead Poisoning in the Ancient World..” Medical History 17 (4): 391–99.

Public Domain Theriaca 002.jpg Created: 10th century

Around 1,000 new cases of lead poisoning diagnosed in Britain in 1900

Lead poisoning data.png

Lead poisoning data.png

McElvenny et al. 2015. “Mortality of a Cohort of Workers in Great Britain with Blood Lead Measurements..”

Occupational and Environmental Medicine 72 (9): 625–32.

WWI

WWII

HSW Act

Occupational exposure limit

0.2mg/m3

The recommended limit for Pb in air in 1921

Threshold Limit Values…• The first systematic list of “modern” OELs was published in

1946 by ACGIH

• 144 Maximal Allowable Concentrations

• Not until 1956, was the term Threshold Limit Value (TLV) used

• In the 1940s the MAC for Pb was 0.15 mg/m3

• 1953 it was made clear these were average concentrations over an 8-hour working day

TLVs become widely accepted…

• By the 1970s many countries or groups had adopted

TLVs or produced their own limits

• In 1948 William Yant, first president of the AIHA

warned, mandatory limits were usually minimum

requirements, “representative of the worst

permissible conditions”

Ziem, G E, and B I Castleman. 1989. “Threshold Limit Values: Historical Perspectives and Current

Practice..” Journal of Occupational Medicine. 31 (11): 910–18.

The essence of occupational hygiene

• Hygienists assess (measure) exposure

• We assume risk is associated with

exposure

– There is an exposure-response

curve

• If exposure exceeds an agreed

threshold then conditions are

unacceptable

Legislation and compliance…

EU Chemical Agents Directive (1998)

“where an occupational exposure limit value effectively established on the

territory of a Member State has been exceeded, the employer shall

immediately take steps, taking into account the nature of that limit, to

remedy the situation by carrying out preventive and protective measures.”

Carcinogens and Mutagens Directive

“Exposure shall not exceed the limit value of a carcinogen as set out in

Annex III.”

http://treball.gencat.cat/web/.content/09_-_seguretat_i_salut_laboral/documents/05_-_promocio_i_campanyes/Jornades/Arxius/EN_689/01.Raymond_Vincent_EN689_Barcelona_Nov_2016.pdf

Do users understand OELs?

…most employers rely heavily on information from suppliers and

personal experience and rather less on “official” information

“The very low understanding and use of OELs reported in this

survey calls for a reappraisal of the OEL system and its

contribution to securing the aims of good occupational hygiene

practice.”

Topping MD, Williams CR, Devine JM. Industry's perception and use of occupational exposure limits.

Ann Occup Hyg 1998 Aug 1;42(6):357–66.

Some problems with OELs…

• Compliance focusses attention on worst situations

• Setting limits may get mired in legal argument

• There may be insufficient human or animal toxicology

data to set a limit

• Employers don’t measure exposure levels

• Exposures are much higher than a health-based limit

Does “compliance” protect health?

Something is working…

Creely KS et al. (2007) Trends in inhalation exposure--a review of the data in the published scientific literature. Ann Occup Hyg.; 51(8): 665-678.

Kaizen = “change for the better”

改善 is the Japanese word for “continual improvement”

OELs become (almost) pointless…

• Put emphasis on continually reducing exposure for the

whole working population

• Success is now measured by the annual percent

reduction in exposure for an industry sector

• Provide targets with a backstop to deal with the

criminals

nepSi.eu

• European Network for Silica, formed by

employee and employer associations

• Agreed appropriate measures to improve

working conditions through good practice,

with training for workers

• Monitoring exposure and provision of health

surveillance

Tuomi T, Linnainmaa M, Väänänen V, Reijula K. Application of good practices as described by the NEPSI agreement coincides with a

strong decline in the exposure to respiratory crystalline silica in Finnish workplaces. Ann Occup Hyg; 2014 Aug;58(7):806–17.

nepSi.eu in Finland

Acceptable and

tolerable risks…

• Risk-based concept for

carcinogenic substances at

work in Germany

• Risks for a working lifetime

– 8 hours per day over a working

life of 40 years.

http://www.baua.de/en/Topics-from-A-to-Z/Hazardous-Substances/TRGS/TRGS-910.html

Tolerable

Concentration of a substance with a risk of 4:1,000

Corresponds roughly to the lung cancer risk for non-smoker

Exposure must be below this limit

Acceptable

Concentration of a substance with a risk of 4:10,000

From 2018 reduced to 4:100,000

Corresponds to cancer risk from environmental risk

Conclusions…

• OELs are necessary but not sufficient to protect worker health

• Exposures generally decrease over time

• Continuous improvement is an alternative to compliance

• Exposure monitoring to assess progress